25 years ago, in December 1972, the United States' last manned lunar
mission touched down upon the Moon. Apollo 17 visited an interesting
area 30 km south of the crater Littrow on the southeastern shore of
Mare Serenitatis near its mountain border. On photographs taken from
orbit, numerous craters encircled by dark haloes can be seen in the
vicinity - at the time, some excited geologists cited these features
as strong evidence favouring lunar volcanism.
Northwest of the landing site is the slender Littrow Rille which
intersects a system of rilles on the border of Mare Serenitatis near
the small impact crater Clerke. These rilles were produced by the
pulling apart of the lunar crust and faulting and they can be
observed through a 150 mm reflector under favourable conditions.
Through a telescope the area appears striated, and some have
speculated that this form of landscape (and areas like it)
constitutes proof of lunar glaciation in the remote past! Sadly,
there is no evidence that the Moon ever went through its own Ice Age,
but there may some ice on the floors of perpetually shadow filled
craters at the Moon's south pole - this question may be answered by
the Lunar Prospector probe in the near future.
Apollo 17 lunar module Challenger landed in a valley between two
large mountain massifs - both visible in small telescopes - setting
down just 200 metres from the planned site. The last Moon walkers
were Eugene Cernan and Harrison Schmitt, the latter being the only
qualified geologist to have visited the Moon.In the lunar rover,
Cernan and Schmitt drove towards the base of South Massif across
light coloured material deposited by a lunar avalanche triggered by
the Tycho impact 100 million years ago.
Observing the region at full Moon you can easily see Tycho in the southern uplands, surrounded by bright rays that stretch hundreds of kilometres across the lunar disc - imagine the tremendous jolt the Moon must have received from the impact. Bedrock was exposed on the mountainside where Moonquakes had shaken off its covering of soil, and boulders had rolled down the mountain slopes, leaving trails. One specimen of rock found here contains material dating back almost to the birth of the Moon. One surprise discovery was that of orange soil, initially thought to be a sign of recent vulcanism. However, the stuff turned out to consist of microscopic glassy beads which were produced in the heat of a meteoritic impact. At North Massif a number of boulders had clearly rolled downhill - around twenty million years ago in this case, yet the imprints in the soil still appeared fresh! One such object, named the Station 6 boulder, was originally a giant 15 metres in diameter, but had split into several pieces. On the final excursion in the lunar rover, the astronauts visited the Sculptured Hills - features believed to be huge mounds of ejecta deposited around 4.2 billion years ago after the asteroidal impact which created the Serenitatis basin. During a stay of more than three days a total of 23 hours of exploration was achieved, in which Cernan and Schmitt had traversed 30 km and collected 110 kg of lunar rock and soil samples. Through a telescope you can spend countless hours contemplating the Apollo 17 site, the last lunar outpost, as if your eyepiece were the porthole of your own spacecraft hovering high above the Moon. Best dates for observation of the Apollo 17 site are the evening of 5 December and morning of 19 December.
